1. Field of the Invention
The present invention relates to an interactive communication system. Specifically, it relates to an interactive communication system, a communication equipment and a communication control method, in this system. According to this interactive communication system, in the case where communications are implemented while other optional data is embedded in voice coded data, for example, in an interactive packet voice transmission system, etc., control information that is used for a control of communications from a transmission side to a reception side and that is obtained on the reception side is embedded instead of the other optional data and then this embedded data is transmitted to the transmission side, thereby controlling the communications on the transmission side using the control information.
2. Description of the Related Art
Along with the popularization of a computer and the Internet in recent years, an electronic watermark technology of embedding special data in multimedia contents (still image, animations, audio, voice, etc.) has been paid attention to. In many cases, such a technology aims at copyright protection that prevents illegal copy or falsification of data by embedding the name of a producer or a distributor of the contents in the contents. In addition, this technology aims at increasing the user's convenience when he or she uses the contents by embedding information related to the contents and additional information.
Also, in the field of a voice communication such as VoIP (voice-over IP) used as a technology of transmitting and receiving voice data using an IP (Internet protocol) network, a system of embedding optional data in voice data and transmitting the thus-embedded data is used. FIG. 18 shows a conventional example of a voice communication system to which such a technology of embedding data is applied.
In, FIG. 18, a voice codec (coder) 50 embeds the optional data series other than voice in a voice code and transmits the thus-embedded code to a communication partner side at the time of coding the input voice from a user 1 into a voice code. If data can be embedded without changing the format of the voice code at that time, the information amount of the voice code is not increased.
A decoder 51 extracts the embedded optional data series from the transmitted voice code and at the same time it outputs the reproduced voice to a user 2 based on a general decoding operation. If the embedding of data is implemented without exerting an influence on the quality of the reproduced voice, there is almost no difference between the voice quality of the reproduced voice and that before the embedding operation is implemented. According to the above-mentioned configuration, optional data can be transmitted separately from the voice without increasing the transmission amount of data. Therefore, for the third person who does not know that data is embedded, this transmission is recognized as a general voice communication.
Furthermore, the various methods are used for the improvement of transmission efficiency and voice quality in a voice communication system. As one of these improvement methods, there is a method of implementing a transmission control on a transmission side utilizing the information that is obtained on a receive side. For example, a method of suitably changing the amount of information that is transmitted according to the condition of a transmission path (communication line) is used. FIG. 19 shows the first conventional example of a voice communication system that implements such a transmission control. In order to simplify the explanation in FIG. 19, the control information that is used for the control of the communications from a side A to a side B is obtained on the side B as B-side information, but it is natural that the reverse case is present.
In FIG. 19, information about the condition of a transmission path can be obtained on the side B from the information about voice data that is received from the side A. For example, in VoIP, information about the delay, the fluctuation and the error rate of a transmission path can be obtained from the header information of a transmission packet. These pieces of transmission path information are transmitted to the side A via a control data circuit and they are used on the side A for a transmission control by a transmission control unit 52.
In this way, it is possible to implement a suitable transmission control. For example, in the case where the load of a transmission path is large, a voice line is first secured by decreasing a transmission amount even if sound quality deteriorates. Furthermore, in the case where the load is small, sufficient sound quality is secured by increasing the transmission amount.
FIG. 20 shows the second conventional example of an interactive voice communication system that implements such a transmission control. In the same drawing, the B-side information is not transmitted to the side A via an exclusive control data line as shown in FIG. 19 but it is multiplexed together with voice data by a multiplexing unit 53 using a multiplex line and then the thus-multiplexed data is transmitted. Subsequently, the transmitted data is demultiplexed by a demultiplexing unit 54 on the side A to be used for a transmission control.
There are following four documents as conventional technologies related to the embedding of data. At first, a document 1 discloses an image coding apparatus that embeds the other kind of information in image information for one screen and compression-codes the embedded information. In other words, this technology discloses a technology of replacing the subordinate digit of the transformation coefficient that satisfies a specified criterion in respect of alternate components, with the partial information that is clipped from the other information, from among transformation coefficients generated by discrete cosine transformation.
In a document 2, a voice communication method of implementing communications by embedding the bits that configure data obtained by coding character information, image information, etc. in low n bits of digital voice data.
A document 3 discloses a technology of transmitting nonverbal information with the bit that is assigned to the output or outputs of one or both codebook(s) by setting the gains of an adaptive codebook and a fixed codebook that are described later at 0 in preferred embodiments of the present invention while targeting a radio voice channel.
A document 4 discloses an electronic watermark technology using a specified key that is shared with a transmission side and a reception side while targeting a CELP (code excited linear prediction) coding system which is described later.
Document 1: Japanese patent application laid-open publication No. 2000-287209, “Image coding apparatus, image decoding apparatus, image coding method and image decoding method”
Document 2: Japanese patent application laid-open publication No. 9-214636, “Voice communication method and apparatus of embedding data”
Document 3: Japanese patent application laid-open publication No.2000-209663, “Method of transmitting nonverbal voice information on voice channel”
Document 4: Japanese patent application laid-open publication No. 11-272299, “Embedding method of watermark bit when voice is coded”
The following is the explanation of the problems of the above-mentioned conventional technologies. First of all, in the conventional examples explained in FIGS. 19 and 20, an exclusive control data line is required or multiplexed transmission with voice information is required in order to transmit control information from a reception side to a transmission side. Therefore, there is a problem such that another transmission path is secured or the increase of transmission amount for the transmission of control information in addition to the voice information should be considered as mentioned above.
In the documents 1 and 2, an embedding parameter such as the embedding position of other data in image data or in voice data is defined in advance on a transmission/reception side and then the embedding and extraction of data are implemented. In the case where the embedding position of such data, for example, the value of n is changed in the document 2, it is necessary to transmit the changed value as a control parameter from, for example, a transmission side. In the case where such data disappears due to the condition of a transmission path, there arises a problem such that it is difficult to precisely determine on a reception side in which position of the received voice code the data is embedded.
It takes a time for a transmission parameter to return to a normal value especially in the case where the condition of the past frame effects on the condition of the present frame. In respect of voice data, an error concealment technology of preventing the extreme deterioration of the sound quality can be also applied but problems regarding the transmission parameter or embedded data still remain.
Furthermore, in the documents 2 and 3, there is a problem such that the deterioration of a voice signal is generated due to the size of the value of n. Also in the document 4, there is a problem such that the possibility of voice deterioration by embedding data is high since the presence or non-presence of data is controlled with probability corresponding to the position of the pulse of a fixed codebook in addition to a problem such that data can be falsified or the like by stealing a key.
The subject of the present invention is to implement a control of communications from a transmission side to a reception side by neither additionally securing a transmission path for transmitting the control information nor increasing a transmission amount due to the control information utilizing the information that is obtained on the reception side while the above-mentioned problem is considered and the format of voice code data remains as it is.
Another subject of the present invention is to prevent the disappearance of the embedded data by re-transmitting the embedded data even in the case where a communication error is generated due to the condition of a transmission path.